1. Field of the Invention
The present invention relates to a thin-film electrode layer for supplying an electric current to a magnetoresistive element, a thin-film magnetic head using a thin-film electrode layer, and a method for forming electrodes in a thin-film magnetic head.
2. Description of the Related Art
Thin film magnetic heads having magnetoresistive elements include thin-film electrode layers for supplying electric current to the magnetoresistive elements. When electric current is supplied to a magnetoresistive element, the resistance of the magnetoresistive element changes, and a leakage magnetic field from a recording medium can be detected by a change in voltage due to a change in resistance. The thin-film magnetic head preferably has thin-film electrode layers composed of a metal having a small resistivity, such as gold, so as to reduce the electrical resistance of components other than the magnetoresistive element.
FIG. 29 is a cross-sectional view showing the structure of electrodes of a conventional thin-film magnetic head. Each of thin-film electrode layers E′ is a composite consisting of a first tantalum (Ta) layer 31′, a gold (Au) layer 33′, and a second Ta layer 34′, stacked in that order. The first Ta, layer 31′ prevents the Au layer 33′ from diffusing, and the second Ta layer 34′ prevents smearing.
However, the above-described conventional Ta/Au/Ta electrode structure has a problem with electromigration (EM) resistance. When a current is supplied to the thin-film electrode layer E′ for a long period of time, i.e., when the thin-film magnetic head is used for long time, Au atoms of the Au layer 33′ drift due to collisions with electrons moving in the thin-film electrode layer E′. For example, when current flows in I direction in FIG. 29, i.e., from right to left in the drawing of FIG. 29, electrons (e−) travel from left to right, thereby producing voids inside an end region S of the thin-film electrode layer E′. This increases the electrical resistance of the thin-film electrode layer E′ despite the use of gold which has a small resistivity.